The objective of this study is to develop a small portable handheld system capable of objectively determining audiogram configurations in infants using auditory steady-state responses (ASSRs). The system will address the need to obtain frequency-specific hearing threshold information in infants less than six months of age in a fast and efficient manner in order to fit hearing aids. Although current ABR technology can also be utilized to determine frequency specific thresholds, tone burst ABRs require expert interpretation and long or multiple testing sessions. Furthermore, current handheld screening devices do not provide frequency specific threshold information. ASSRs allow the application of objective frequency domain response detection analysis techniques that are capable of providing fast and accurate frequency specific hearing threshold information which is required for hearing aid fitting in infants. The proposed system will further improve current ASSR testing techniques by implementing advanced threshold estimation routines in order to reduce testing time. During Phase I, a fast audiogram estimation technique, CAST (Classification of Audiograms by Sequential Testing), was adapted from behavioral to ASSR testing and was shown to be very efficient and accurate. The ASSR testing module developed during Phase I was integrated into an evoked potential and otoacoustic emission testing system which has received FDA approval and is currently being distributed. During Phase II, further refinement of the ASSR CAST technique will be continued and a new ASSR Intensity-Ramping technique will also be refined and tested. The ASSR testing module will be implemented in a miniaturized handheld hardware unit providing greater portability for screening and testing applications at a very competitive price. The portable device will also provide standard ABR and OAE testing with in-ear calibration options for all testing modalities. A large-scale clinical trial will be conducted during the second year of Phase II involving three major testing sites.